is it a ground loop if the hum isnt constant?

[jason]

i really need some help:

ive been having this problem for a long time, ever since i incorporated the DVR and cable modem into my home theater set up:

i get a hum/buzz, but not all the time, it comes and goes, i can be watching tv for like an hour, then all of a sudden.. "HUMMMMMMMMMMMMMM"

so i turn the receiever off, wait a minute, turn it on, and its usually gone, but of course it comes back

i get the hum on all input channels on the receiever, changing the volume level does not alter the level of the hum

i have tried unplugging from the wall outlets, one by one, every single component in my setup while the hum is occurring..

once i unplugged every single component except the receiver and the noise was still there, so i unscrewed the coaxial cables connecting the CATV outlet from the wall and the DVR box, instantly the hum got way LOUDER, i then put one hand on the connectors of each coaxial cable, and the hum got super quiet almost completely gone

so yeh it kind of sounds like a ground loop problem, but also im wondering if perhaps my CATV outlet was simply not grounded properly when the home was built

i tried using a Jensen RF Digital Cable Isolator installed at the wall outlet, which is supposed to lift the CATV ground therefore solving the problem if its a ground loop, but it only made the hum WORSE

if youve read this far, thank you, id greatly appreciate any input/advice/suggestions

 

[jonnythan]

Are you saying the hum is there with nothing at all plugged into the receiver?

 

[j_garcia]

Ground loop doesn't have to be from the wall to the box, it can be between the box and the receiver, so if you disconnect the DVR to the receiver does it go away?

 

[jonnythan]

My general advice would be to unplug absolutely everything but the speakers from the receiver. Start plugging in wires one by one, while it's on, and figure out which wire causes it to start humming.

If it's humming with no inputs at all plugged in, the receiver is broken.

 

[mtrycrafts]

i tried using a Jensen RF Digital Cable Isolator installed at the wall outlet, which is supposed to lift the CATV ground therefore solving the problem if its a ground loop, but it only made the hum WORSE

After you respond to jgaria's question, you need to check for another path from the cable TV setup and your receiver. I bet there might be another path someplace.

Looks like this started with that DVR installation. Maybe you need to move that Jensen isolator at another location to block the ground-loop from the receiver?

 

[dave1490]

i really need some help:



once i unplugged every single component except the receiver and the noise was still there, so i unscrewed the coaxial cables connecting the CATV outlet from the wall and the DVR box, instantly the hum got way LOUDER, i then put one hand on the connectors of each coaxial cable, and the hum got super quiet almost completely gone


this happends when you have alot of em "soup" in close proximity{hard drives,speakers,tv,monitors ect}if you ever put your arm close to a tv and seen your hairs stand up,you know what i mean.id just get shieded cables,they also fix snow if you have that.{the hum get,s quieter because it,s useing your body as a ground.}

 

[zumbo]

Check where your cable comes from the pole to the house. The cable has a small ground wire. The cable looks like a 8. The little wire in the jacket is the ground. Cut it. Only it. Peel it back to remove a small section. Do not expose the large wire.

I have mine done this way. I did it up on the roof, so the cable company has no idea the ground is missing. They will reconnect it if they find it tampered with.

 

[zumbo]

This works for poison ivy as well. If poison ivy is taking over a tree, cut a chunk out of the large vine at the bottom part of the tree (about a foot), and the whole vine will die.

 

[mtrycrafts]

I doubt that happens with the LCD, DLP or Plasma TVs. But, yes, it does happen with CRTs and it isn't what you stated, EM, but the very high voltages that is on the picture tube and creates static electricity and makes your hair stand up.

 

[mtrycrafts]

Check where your cable comes from the pole to the house. The cable has a small ground wire. The cable looks like a 8. The little wire in the jacket is the ground. Cut it. Only it. Peel it back to remove a small section. Do not expose the large wire.

I have mine done this way. I did it up on the roof, so the cable company has no idea the ground is missing. They will reconnect it if they find it tampered with.

That is not a good suggestion. It can be dangerous too. And, they may prosecute?

 

[zumbo]

That is not a good suggestion. It can be dangerous too. And, they may prosecute?

Who can prove (I, you, OP) cut the cable?

From the following link:
Fixing the Problem
There are at least two practical ways to fix the problem of a ground loop in your system. Once you know the problem is related to the Cable TV ground and the amplifier ground, as it is in this case (and lots of cases) you can lift the Earth ground on either device at the line level. I find it much easier to lift the ground on the Cable TV line than on 5.1 multi-channel inputs going into the amplifier!

http://www.audioholics.com/techtips/setup/avhardware/groundloopcableTV.php

 

[mtrycrafts]

Who can prove (I, you, OP) cut the cable?

From the following link:
Fixing the Problem
There are at least two practical ways to fix the problem of a ground loop in your system. Once you know the problem is related to the Cable TV ground and the amplifier ground, as it is in this case (and lots of cases) you can lift the Earth ground on either device at the line level. I find it much easier to lift the ground on the Cable TV line than on 5.1 multi-channel inputs going into the amplifier!

http://www.audioholics.com/techtips/setup/avhardware/groundloopcableTV.php

Yes, that link mentions a cable TV ground isolator from Jensen, the one the poster is having problems with. Perhaps it is in the wrong place, or needs another at another location.

 

[zumbo]

Yes, that link mentions a cable TV ground isolator from Jensen, the one the poster is having problems with. Perhaps it is in the wrong place, or needs another at another location.

I used an isolater with regular cable. But, when I switched to digital cable, the isolater proved useless. Don't know why. Might have had something to do with the cable box. So, I disconnected the ground. Works like a champ.

 

[jason]

Ground loop doesn't have to be from the wall to the box, it can be between the box and the receiver, so if you disconnect the DVR to the receiver does it go away?

it does not

i should also point that a cable modem and router and connected in the same system

ive tried at one point disconnecting them all, from the wall outlet and from the receiver inputs, but still the hum is present

 

[jason]

If it's humming with no inputs at all plugged in, the receiver is broken.

this was my thoughts at first too but it just doesnt add up

its an almost new receiver, barely 2 years, and it hasnt seen any abuse, an Onkyo 602

also, as stated in original post, with everything unplugged, and the hum coming through, i can mute it considerable by simply touching the CATV outlet on the wall (this is located approx 12inches behind the central part of the home theater setup)

 

[jason]

After you respond to jgaria's question, you need to check for another path from the cable TV setup and your receiver. I bet there might be another path someplace.

Looks like this started with that DVR installation. Maybe you need to move that Jensen isolator at another location to block the ground-loop from the receiver?

yeh there is multiple paths, because there is also a cable modem and router

i have only tried placing the isolator in the one place, ill go ahead and move it around and see if that produces better results

 

[jason]

i really need some help:



once i unplugged every single component except the receiver and the noise was still there, so i unscrewed the coaxial cables connecting the CATV outlet from the wall and the DVR box, instantly the hum got way LOUDER, i then put one hand on the connectors of each coaxial cable, and the hum got super quiet almost completely gone


this happends when you have alot of em "soup" in close proximity{hard drives,speakers,tv,monitors ect}if you ever put your arm close to a tv and seen your hairs stand up,you know what i mean.id just get shieded cables,they also fix snow if you have that.{the hum get,s quieter because it,s useing your body as a ground.}

this seems to make a lot of sense..

i should point out that all audio cables on my setup are optical

every single cable in my setup, audio and video, is made by Acoustic Research, the brand you get at Best Buy, i assumed these were shielded, would you know offhand if they are or not?

 

[jason]

the isolator im using is from the link Zumbo posted, its designed for digital cable setups

it seems right now all i can try to do is move the isolator around and see if anything changes and get back to you guys with the results

before posting here i read and re-read that article on ground loops but i couldnt get to the bottom of the problem

thanks to everyone for the advice!

keep those questions and suggestions coming

 

[mtrycrafts]

yeh there is multiple paths, because there is also a cable modem and router

i have only tried placing the isolator in the one place, ill go ahead and move it around and see if that produces better results

Or, you may need several of those isolators so the grounding issue doesn't sneak in. But, at least try it in other locations first; you might find the critical location.